\psset{unit=0.7,algebraic}
\begin{pspicture*}(-5,-3)(5,3)
\psaxes[labelFontSize=\scriptstyle,ticksize=-3pt 0,labelsep=2pt]{<->}(0,0)(-3,-3)(3,3)
\psplot[linecolor=blue]{-2}{2}{x^2-2}
\normalsize
\rput[l](1,2.5){$f(x)=x^2-2$}
\uncover<2->{
\psline[linecolor=red,linewidth=1pt,tbarsize=7pt 0,arrows=[->](0,-2)(0,3)
}
\end{pspicture*}